CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income/(loss)	$ 64,358	$ (16,523)	$ 97,377	$ (5,626)
Other comprehensive (loss)/income, net of tax:
Net change in unrealized losses on cash flow hedges	(1,183)	(7,203)	(16,168)	(10,381)
Defined benefit pension and other postretirement benefit plans:
Net change in unrecognized prior service costs	8	30	80	4
Net change in unrecognized actuarial losses	56	197	577	24
Other comprehensive loss, net of tax	(1,119)	(6,976)	(15,511)	(10,353)
Comprehensive income/(loss)	$ 63,239	$ (23,499)	$ 81,866	$ (15,979)